Astragalus congdonii S.Watson
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Authors
Rupert C. Barneby
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Authority
Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(1): 1-596.
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Family
Fabaceae
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Scientific Name
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Type
"At Hite’s Cove on the Merced River, Mariposa County, California, collected by J. W. Congdon, June, 1883."—Holotypus, GH! isotypus, NY!
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Description
Species Description - Diffuse, usually rather coarse but sometimes quite slender, villous-villosulous nearly throughout with widely ascending, straight, incurved, or ± sinuous (and often some shorter, curly), white (and toward the inflorescence often partly fuscous) hairs up to 0.9-1.4 mm. long, the stems and herbage either equally greenish-cinereous, or the stems, and sometimes the young herbage, white-villous- tomentulose, the leaflets equally pubescent on both sides or more thinly so above; stems several or numerous, decumbent and ascending from the pluricipital root- crown or shortly forking caudex, (1) 1.5-7.5 dm. long, striate, green or purplish- tinged, nearly always branched or spurred at 1-3 (4) nodes preceding the first peduncle, simple only when short and slender, floriferous upward from near or below the middle; stipules thinly herbaceous, the lowest becoming papery, fragile and brownish in age, ovate-, triangular- or lance-acuminate or -caudate, 2-8 mm. long, ± semiamplexicaul, pubescent dorsally, ciliate, the blades commonly squar- rose; leaves spreading-recurved, (3) 4-12 (14) cm. long, the lowest shortly petioled, the upper ones sessile or nearly so, with (11) 17-35 (37) oblong-elliptic, ovate, obovate, or (especially in some lower leaves) suborbicular, truncate, retuse, retuse and mucronulate, rarely subacute, flat or loosely folded leaflets 3-15 mm. long, dorsally carinate by the midvein, diminishing upward along the rachis; peduncles either stout or (all or some upper ones) quite slender, (5) 7-18 (20) cm. long, surpassing the leaf; racemes loosely or at length remotely (8) 12-30 (35)-flowered, the flowers early spreading, ultimately declined, the axis elongating, (3.5) 5-20 cm. long in fruit; bracts submembranous, triangular- or narrowly lance-acuminate, 1.2-3.4 mm. long; pedicels at first ascending, straight or nearly so, 0.3-1.5 (2) mm. long, in fruit thickened, recurved, 0.5-2.2 (3) mm. long; bracteoles 0-2, minute when present; calyx 5.3-7.5 (8) mm. long, villosulous with fuscous, black, or partly white hairs, the subsymmetric to strongly oblique disc. 0.9—1.5 mm. deep, the membranous, pallid or purplish, broadly or narrowly campanulate tube 3.8—5 (5.3) mm. long, 2.5—4.2 mm. in diameter, the subulate or triangular-subulate teeth 1.1—2.5 (3) mm. long; petals white or whitish, immaculate, drying ochroleucous; banner recurved through ± 45°, broadly or narrowly oblanceolate, elliptic-oblanceolate, or rhombic-elliptic, shallowly or deeply notched, 10.4—15.6 (16.6) mm. long, 4.8—7 mm. wide; wings (shorter or rarely a trifle longer) 9-15 (16.2) mm. long, the claws 3.6-6.7 (7) mm., the linear-oblong or oblanceolate, obtuse, truncate-erose, or obliquely emarginate, slightly incurved blades 6.4—10 (10.4) mm. long, 2—3.4 (3.8) mm. wide; keel 7.4-12.7 mm. long, the claws 3.5-6.8 mm., the half-obovate blades 4.5-6.8 mm. long, 2.4-3.6 mm. wide, incurved through 90-95° to the bluntly deltoid apex; anthers (0.45) 0.5—0.75 mm. long; pod declined, the straight, glabrous or puberulent stipe 1—2.5 mm. long, concealed by the marcescent calyx, the body Unear in outline, nearly straight to falcately incurved through ± 1/3 -circle, (1.5) 2-3.5 cm. long, 2.3—3.2 mm. in diameter, abruptly cuneate at base, contracted distally into a short, triangular, cuspidate, unilocular beak, otherwise compressed-triquetrous, with low-convex lateral and slightly narrower, deeply but narrowly grooved dorsal faces, carinate ventrally by the prominent suture, the lateral angles obtuse, the thinly fleshy, green or purple-tinged valves becoming stiffly papery, stramineous, finely cross-reticulate, densely to quite thinly strigulose-villosulous with subap- pressed, ascending and nearly straight, or looser and sinuous hairs, the complete or nearly complete septum 1-2 mm. wide; ovules (17) 23-29; seeds purplish- or chestnut-brown, or greenish, often purple-speckled, pitted, wrinkled, or both, scarcely lustrous, 2.2—3 mm. long.
Distribution and Ecology - Open brushy banks, canyon sides, and road cuts, commonly on and perhaps confined to metamorphic, sometimes partly serpentinized bedrock, 550-2000 feet, uncommon, scattered within and slightly below the digger pine belt in the Sierra Nevada foothills from the Mokelumne south to the Tule River, Amador to Tulare County, California.—Map No. 50.—March to May (June).
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Discussion
In contrast to the rich development of the genus elsewhere in California, the astragaline flora of the Sierra’s west slope is unexpectedly poor. In fact the Congdon milk-vetch is the only perennial astragalus known from the segment of Low Foothills (as defined by Jepson, 1925, p. 13) that extends from the Yuba River south to the Kern-Tulare County line. The species, far from common, consists of six or seven main populations concentrated into small areas in the valleys of the Mokelumne, Stanislaus, Tuolumne, Merced (both North and South Forks, immediately below Yosemite), Kings and Tule Rivers. The plants of A. Congdoni that J. T. Howell and I saw in the type-locality at Hite’s Cove grew on a recently burned-over slope; at Piedra on Kings River, we saw an especially vigorous form only on road-cuttings and on debris under cliffs. Possibly the species requires, or at least prefers, a disturbed or unstable habitat. In both these stations the Congdon milk-vetch is associated with outcrops of metamorphic bedrock, and this may prove to be the factor determining its discontinuous dispersal. Isolation of the colonies may have favored different modes of variation from one valley to the next. The species is very variable in stature, density of vesture, size of flower, and length of pod, but its essential structural features are uniform. The nearest relatives of A. Congdoni are A. agnicidus and A. umbraticus of the outer Coast Ranges; the relationship, however, is not really close. The copious, loose pubescence, the open, secund racemes of white flowers, and the long, narrow, hanging pods are distinctive.
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Objects
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Distribution
California United States of America North America|